1. Field of the Invention
The present invention relates to a magnetic head for recording signals on and reproducing signals from a magnetic recording medium such as a magnetic disc or a magnetic tape while slidably moving thereon, and more particularly to a thin-film magnetic head suitable for recording signals on and reproducing signals from a small-size magnetic recording medium.
2. Description of the Prior Art
There have heretofore been developed various magnetic recording and reproducing apparatuses for recording various signals on and reproducing various signals from magnetic recording mediums. In recent years, with the miniaturization of magnetic recording mediums, efforts have also been made to develop magnetic heads suitable for recording information signals on and reproducing recorded information signals from a variety of such magnetic recording mediums. For example, there is known a small-size disc-shaped magnetic recording medium in which the innermost circular recording track has a radius of 15 mm and the outermost circular recording track has a radius of 20 mm. The magnetic heads for recording signals on and reproducing signals from such small-size disc-shaped magnetic recording mediums are required to be smaller in size and to suffer reduced crosstalk. To meet these requirements, thin-film magnetic heads are used more and more frequently in place of conventional bulk-type magnetic heads. The thin-film magnetic heads can be fabricated in miniature size for multichannel recording and reproducing capability and lowered crosstalk. The thin-film magnetic heads are especially finding use as narrow-track magnetic heads for recording signals in a high track density.
As shown in FIG. 5 of the accompanying drawings, one known thin-film magnetic head is composed of upper and lower magnetic layers 2, 4 deposited as thin films on a substrate 1, the upper and lower magnetic layers 2, 4 serving as magnetic poles. For the prior thin-film magnetic head to have a very small track width, the upper and lower magnetic layers 2, 4 have to be shaped to make their track widths smaller than the yoke length. In the magnetic layer in which the yoke length is larger than the track width, however, spontaneous magnetization in the magnetic layer tends to be oriented in a direction parallel to the yoke length due to geometric anisotropy. Therefore, when responding to the magnetic fluxes generated by signals recorded on the magnetic recording medium in a playback mode, or the external magnetic fluxes produced by currents flowing in a recording mode, the magnetic layer is magnetized by movement of the magnetic wall, resulting in a low speed of response in the recording and playback modes. As a consequence, the conventional thin-film magnetic head has a reduced magnetic efficiency and a lowered signal-to-noise ratio in the high-frequency range, and suffers higher Barkhausen noise in signal reproduction. Another problem is that since the upper magnetic layer has a small cross-sectional area, the magnetic head is magnetically saturated in the vicinity of the gap when recording signals on the magnetic recording medium, with a resulting reduced recording efficiency.
In the conventional thin-film magnetic head design, the magnetic layers are deposited on the substrate employed as a lamination support. When the magnetic head slides against the magnetic recording medium, the substrate sometimes damages the magnetic recording medium, causing an error in reading signals therefrom.